CHEVY OVERHEATING

i have a 93 chevy lumina 3.1 l I have a problem with overheating, I already check the water pump, thermostat and the radiator cap and radiator and they are working fine, I dont know whatelse could it be. Thanks for your help

Are you losing coolant? Is there oil mixed in radiator or coolant mixed in oil? An easy way to check for cracked head gasket is to remove radiator cap (while COLD) then start engine ( MAKE SURE NOONE IS AROUND RADIATOR). If coolant shoots out of radiator then you have a head gasket or head cracked.